The field of this invention is orthopaedics.
Since its development in the 1960s, total hip arthroplasty has become an important procedure in the field of orthopaedics, and has been characterized as the xe2x80x9cgreatest single advance in modem orthopaedic surgery.xe2x80x9d See Finerman, infra. Currently, approximately 125,000 hip replacements are performed in the United States alone each year, where the total cost of such procedures in the United States has been estimated to exceed $3 billion.
As such a variety of devices have been developed for use in hip replacement procedures. Like the natural hip, a hip replacement device consists of a ball and socket joint. Hip replacement involves the implantation (with or without cement) of a metal component having a ball on the upper (proximal) end into the proximal femur and the implantation of a plastic socket component into the pelvis (acetabulum). Loosening leads to pain and bone destruction resulting in the need for surgical revision. Loosening has been attributed to unnatural and inappropriate stresses that exist at the implant collar/bone interface and that exist within the bone (e.g., within the medial femoral cortex).
In an attempt to improve force and stress transfer between implant and bone, many hip replacement designs utilize a collar on the femoral component. Flat collars, as shown in FIGS. 1A and 1B, are one common design. A conical collar, as shown in FIGS. 2A and 2B, has provided improved results and is also currently employed. Other configurations that have been or are currently marketed include the tapered configuration shown in FIGS. 3A and 3B.
While a variety of different configurations have been developed since total hip arthroplasty was first developed, there continues to be interest in the development of new prostheses that can provide for better short- and/or long-term outcomes.
Relevant Literature
Total hip arthroplasty (as well as devices for use therein) is reviewed in Finerman et al., Total Hip Arthroplasty Outcomes, (Churchill Livingston, Inc., 1998).
U.S. Pat. Nos. of interest describing different hip devices include: 5,725,594; 5,702,485; 5,387,244; 5,376,124; 5,336,265; 5,330,536; 5,314,489; 5,314,479; 5,197,990; 5,167,666; 5,133,772; 5,116,377; 4,938,771; RE 32,488; 4,661,112; 4,642,124; 4,546,501; 4,514,865; 4,488,320; 4,406,023; and 4,359,785.
Novel prostheses and methods for their use, particularly in hip replacement, are provided. The subject prostheses are elongate devices having a proximal and distal end, where the devices have the following elements going from the proximal to distal end: (a) a ball component; (b) a neck component; (c) a curvilinear collar component; and (d) a stem component. Also provided are methods of implanting hip prostheses in a manner sufficient to provide for a pressure profile at the collar interface in which the pressure increases from the endosteal to the periosteal surface of the bone.